Locking plug for electric circuits



April 1934- F. E. REINHOLD 1,955,146

LOCKING PLUG FOR ELECTRIC CIRCUITS Filed Oct. 20, 1930 9 54 35 3 34 34WIN/? 52 Patented Apr. 17, 1934 it St rss aren't 7 Claims.

This invention relates generally to electrical service equipment, morespecifically to plugs adapted to be positionedin fuse boxes, cut-outs orthe like to replace fuses to form a seal when it is desired todiscontinue service therefrom.

The broad object of this invention is to provide a plug of the typereferred to which cannot be removed from a socket or the like byunauthorized persons.

Another object of this invention is to provide a plug of the characterstated which cannot be removed from a socket except by a special tool.

A further object of the present invention is to provide a plugconstructed in such a manner that it cannot be removed from a socketwith sharp pointed tools, such as chisels or the like.

Other objects and advantages will be apparent from the followingdescription, reference being had to the accompanying drawing, in which:

Fig. 1 is a front elevation of a cut-out block with a plug of thepresent invention in inoperative position in the socket thereon;

Fig. 2 is a cross section taken substantially on line 2-2 of Fig. 1;

Fig. 3 is a section taken through the improved plu Fig. 4 is aperspective view of the upper movable ring forming a part of theimproved plug;

Fig. 5 is a perspective View of the stationary ring secured to the plugbody;

Fig. 6 is a top plan view of a slightly modified form of plug, partsbeing broken away to show other parts;

Fig. '7 is a section taken on line '77 of Fig. 6;

Fig. 8 is a top plan view of a plug showing a modified means of securingthe movable plate to the plug body;

Fig. 9 is a section taken on line 9-9 of Fig. 8;

Fig. 10 is a section taken through the wrench employed to apply orremove the improved plug; and,

Fig. 11 is an end view of the wrench shown in Fig. 10.

Referring more specifically to the drawing, 10 designates a standardcut-out block formed of porcelain or the like including a base 12 havingan annular flange 13 formed thereon in which is mounted a socket 11 inwhich is normally positioned a standard fuse (not shown) which is iadapted to be replaced by the improved plug generally designated at 16.

Socket 11 consists of a threaded sleeve 14 provided with a bottomportion 18 upon which is mounted a disk 19 formed of insulatingmaterial,

1 the sleeve being secured to the base by a bolt 20 and nut 21 whichalso engages a lead 22 extending from a conductor 23, the bolt alsoserving as a center contact for the fuse above referred to, a circuitbeing completed through the fuse by a metal strip 24; positioned betweenthe base 12 and bottom portion of the sleeve and leading to a conductor25.

Referring more specifically to Figs. 3, l and 5, the improved plugconsists of a body portion formed of insulating material, preferablyBakelite, and is externally threaded as indicated at 31 in order that itmay be screwed into the sleeve.

Mounted on the upper face 32 of the body portion is a metallic plate 34which is rigidly held in place thereon by portions of the body portionindicated at 35 extending into apertures 36 having tapered sides,connection between the body portion and the plate being effected whilethe body portion is in a pliable condition.

Positioned on the plate 34 is a rotatable plate 38 which is held inplace thereon by a head 39 of a rivet 40 engaging a tapered opening 42formed in said plate. The head is formed on a shank 43 extending throughan opening 44 formed in the plate 34, the rivet being secured to thebody portion by split or bifurcated ends 45 formed on the shank 43 whichare embedded in the body portion. The plate 38 and head 39 of the rivetare preferably casehardened for a purpose hereinafter described.

The fixed plate 34 has a fiat portion 47 formed in its circular sidewall, and the movable plate 38 has a corresponding flat portion 46formed in its side wall. These fiat portions are provided in order thatthe plug may be inserted into or removed from the socket, a specialsocket wrench designated at (Figs. 10 and 11) being provided for thispurpose.

When applying or removing the improved plug the fiat portions 46 and 47are brought into register so that the wrench 50 may engage the fixedplate 34, the plug may then be firmly screwed into the sleeve. Afterremoving the wrench from the plug, the plate 38 is free to turn upon theshank of the rivet. Hence should an attempt be made to remove the plugwith a sharp tool, such as a chisel or the like, the plate 38 willmerely rotate without having any effect whatever upon removthe plug fromthe socket with tools other than the wrench.

The body portion is provided with a recess 52 to accommodate the centercontact when the plug is screwed into the sleeve, it being understood,however, that the body portion may be formed of conductive material andarranged to engage said contact when it is desired to form a circuit ormake solid through the plug.

Referring to Figs. 6 and '7, a slightly modified form of plug is shown,the construction being exactly the same as above described except thatthe rivet designated at 54 has a shank 55 extending through alignedopenings formed in the plate 38 and body portion, and is held in placeby a head 56 engaging a washer disposed in the recess 52.

The plug illustrated in Figs. 8 and 9 is substantially the sameconstruction as shown in Figs. 1 to '7 inclusive, except that a pin 58is Welded or otherwise secured to the plate 38 as indicated at 59, ahead 60 being formed thereon which serves to hold the parts in assembledrelation.

I claim:

1. A plug comprising an annular body portion formed of insulatingmaterial, a plate secured to said body portion, a second plate rotatablymounted on said first plate, and means for connecting said second plateto said body portion, whereby said second plate may rotate upon saidfirst plate, said first and second plates having surfaces formed thereonadapted to be engaged by a socket wrench for insertion of the plug intoa socket of the character described.

2. A plug comprising a body portion formed of insulating material andexternally screw threaded, a plate secured to said body portion, asecond plate mounted on said first plate, a rivet, said rivet having ahead engaging an opening formed in said second plate, a shank extendingthrough an opening in said first plate, and projections formed on theshank of said rivet embedded in said body portion holding said secondplate in rotatable engagement with said first plate.

3. A plug comprising an annular body formed of insulating material andexternally screw threaded, a metal plate mounted on said body portionand secured thereto by portions of said body portion extending intoapertures formed in said plate, a second metal plate mounted on saidfirst plate, and a member rotatably connecting said second plate to saidbody portion, said first and second plates having fiat portions formedin their circular side walls adapted to be engaged. by a wrench forinsertion of the plug into a socket.

4. In combination with an electric socket including a screw threadedsleeve, of a plug threaded therein, said plug having a plate securedthereinto, and a second plate rotatably mounted on said first plate,said first and second plates having surfaces formed thereon forengagement with a wrench when inserting or removing the plug from thesocket.

5. In combination with an electric screw threaded socket, of a plugthreaded therein having a circular head provided with a mutilatedperiphery, and a circular metal plate having a mutilated peripherycorresponding to the mutilated periphery of the head rotatably securedto said plug head, said head and plate adapted to be engaged with awrench when inserting or removing the plug from the socket.

6. A locking plug for electric sockets and the like comprising acylindrical body portion having a circular head of less diameter thanthe body portion, the periph ry of said head being mutilated, and acircular metal plate of substantially diameter as the head portionrotatably secured thereto, said plate having a mutilated peripherysimilar to the periphery of the head of the body portion.

7. A locking plug for fuse sockets and the like comprising an externallythreaded body portion having a circular head of less diameter than thebody portion, the periphery of said head being mutilated, a circularmetal plate of substantially the same diameter as the head rotatablysecured to said head, the periphery of said plate being mutilatedsimilar to the head of the body portion, and means for temporarilyholding the metal plate in locked engagement with the head of the bodyportion during the insertion of the locking plug into the socket.

FREDERICK E. REINHOLD.

